It is already known to separately control a number of compressors that are part of a compressed air unit by means of a separate controller, whereby the different controllers are not connected to each other, and whereby each of these controllers is set at a different pressure value so as to switch the compressors sequentially on or off, depending on the consumption of compressed air.
It is also known to apply what is called a centralised control, whereby several compressors are controlled by means of a single controller, to which end said controller determines the operational condition of all these compressors at any time.
Finally, also another method for the centralised control of a compressed air unit is known whereby several mutually connected controllers are used to control a number of compressors which are connected to these respective controllers and whereby at least one of these controllers determines the operational condition of each of said compressors at any time.
As a result, one of the controllers can function as a “master” at any time, giving orders to the other “slave” controllers to control the respective compressors connected to the latter.
Another possible application of such a configuration consists in that each of the controllers determines the operational condition of all the compressors and controls is only those compressors connected to it, taking into account the condition of the other compressors.
A disadvantage of the known methods is that they only make it possible to control simple compressed air networks with relatively few components.
Another disadvantage is that such a method quickly leads to the use of complicated controllers, which are expensive and which make the lay-out and control logic of such a compressed air unit relatively extensive and complex, especially when many parameters have to be taken into account.